Automatic merge from submit-queue

proposals: Add Volume Hostpath "type" proposal

This is a continuation of #31384. It's related to #26816 as well.
The discussion in #31384 is worth reading and this proposal largely derives from my comments there.

cc @thockin @pmorie @saad-ali @kubernetes/sig-storage 
cc @yujuhong since it talks briefly about kubelet doing more

cc @calebamiles I think we might need a "Feature" for this since it's an api change, though a minor one?